Taipei: Autopsies on four hikers killed in a rockfall on a Taichung hiking trail confirmed Sunday that they died of traumatic shock caused by falling rocks, prosecutors said. The Taichung District Prosecutors Office stated that prosecutors and forensic examiners conducted the autopsies earlier in the day after the victims' bodies were taken to a funeral home in Taichung.According to Focus Taiwan, the four deaths were ruled accidental, and prosecutors issued death certificates after the victims' families raised no objections to the findings. Prosecutors are continuing to investigate whether the accident involved criminal negligence.The victims were part of a 16-member hiking group organized by the Republic of China Primitive Life Education Association that traveled from Taipei on Saturday to hike the Butterfly Valley Waterfall Trail in Taichung's Heping District, according to police. Rocks struck five members of the group on the trail, killing four and leaving one with minor bruises, police said.The dece ased were identified as the group's guide, a 61-year-old man surnamed Yeh; a 63-year-old man surnamed Cheng; a 69-year-old woman surnamed Yao; and a 57-year-old woman surnamed Chi, police reported. Association Chairman Wu Swei-pi, who organized the trip, mentioned that the weather was clear when the group set out and forecasts had shown no rain was expected in the area on Saturday afternoon.Wu noted that the association had organized monthly hikes for 30 years and had visited the trail many times. He explained that Yeh had turned back to assist slower hikers in crossing a stream when the rockfall occurred. Wu expressed regret over the accident and suggested that warnings or a temporary trail closure could have alerted hikers to the danger.The Taichung Branch of the Forestry and Nature Conservation Agency released a statement on Sunday indicating that the trail remained open because rainfall associated with Tropical Storm Mekkhala had not met the threshold for closure. The agency mentioned that the rockfal l occurred near the 1.2-kilometer mark of the trail, an area with no previous history of slope failure, and attributed the collapse to excessive rainfall. Trail experts will conduct an on-site inspection soon.Authorities are considering closing the affected section and installing slope monitoring equipment, the agency said. Former Transportation Minister Tsai Duei, who was among the hikers, escaped unharmed.